U.S. Pat. No. 4,464,602 issued Aug. 7, 1984 to Joseph Murphy discloses and claims an electroluminescent device comprising an electrically-insulating layer of Y.sub.2 O.sub.3 sandwiched between two electroluminescent layers of manganese-cation-activated zinc sulfide, which composite structure is sandwiched between two electrodes. The electrically-insulating layer is about 4,000 .ANG. thick. The device will emit light when about 70 to 200 volts at about 500 hertz are applied to the device.